1. Field of the Invention
The invention relates to mining, and more particularly it relates to devices for borehole hydraulic mining.
The invention can find application in mining of such minerals as peat, phosphorite, building materials (sand, clay), bauxites, oxidized iron and manganese ores, coal (lignite), development of rare and radioactive metal deposits, as well as placer deposits of gold, diamond, amber, development of submarine deposits, including those in the World Ocean shelf zone, cutting of underground openings of different configuration in barren rocks for laying foundations, draining groundwater, and making underground storages for liquid and gaseous products.
2. Description of the Prior Art
There is known a device for borehole hydraulic mining (SU, A, 1,198,205), comprising a pipeline for delivering water into the hole accommodated inside the pulp lifting pipeline. Secured to the lower end of the pipeline for delivering water into the hole is a hydraulic giant which is in fact a stem with hydraulic jets secured to its lower end. The device also comprises a hydraulic elevator with a water and pulp mixing chamber, and a nozzle secured to the lower end of the pulp lifting pipeline and enclosing the hydraulic giant stem. The hydraulic giant casing is provided with holes whereby the inner space of the hydraulic giant communicates with the inner space of the hydraulic elevator nozzle. Water enters the hydraulic giant under pressure, wherefrom it flows through the hydraulic jets into rocks for mineral disintegration. Part of the water flow enters the hydraulic elevator through the holes provided in the hydraulic giant casing. A water jet emerging from the annular nozzle of the hydraulic elevator and flowing into the water and pulp mixing chamber has an inner space with a rarefaction zone into which the pulp is drawn.
The pulp is drawn from the face of the hydraulic elevator, which results in lower mining efficiency.
Such a constructional arrangement of the device makes it impossible to use a drilling bit required in mining of unconsolidated rocks prone to caving.
There is also known a device for borehole hydraulic mining (SU, A, 1,191,584) comprising a pipeline for delivering water into the hole concentric within which is a pipeline for bringing pulp to the surface. Secured to the lower end of the pipeline for delivering water into the hole is a hydraulic jet hydraulically associated with this pipeline. The device also comprises a hydraulic elevator with a water and pulp mixing chamber secured to the lower end of the pipeline for bringing pulp to the surface and a nozzle secured to the lower end of the pipeline for delivering water into the hole by means of water supply pipes whose one end is secured to the end of the pipeline for for delivering water into the hole and the other end, to the nozzle body. The hydraulic elevator nozzle is positioned below the water and pulp mixing chamber coaxially therewith. The inner space of the hydraulic elevator nozzle is hydraulically associated with the inner space of the pipeline for delivering water into the hole through the ports between the water supply pipes of the pipeline for delivering liquid into the hole.
Part of the water enters the hydraulic jet under pressure, after which it flows into rocks, wherein a mineral is disintegrated and a pulp is formed. The other part of the water flows into the hydraulic elevator nozzle through the water supply pipes. At the inlet to the water and pulp mixing chamber there is formed a rarefaction zone into which the pulp is drawn. Should the need arise to deepen the hole in unconsolidated rocks, use is made of drilling bits secured to the lower end of the pipeline for delivering water into the hole. In the process of hydraulic mining following hole deepening when the drilling bit is not used, water keeps entering the flushing ports of the drilling bit, thereby facilitating water leakage and increasing power expenditure.
The water supply pipes prevent the pulp from entering the water and pulp mixing chamber of the hydraulic elevator, thereby decreasing an active zone of drawing the pulp into the water and pulp mixing chamber of the hydraulic elevator and affecting hydraulic mining efficiency.
In the course of drilling, a torque is imparted to the drilling bit by means of the water supply pipes which are positioned within a certain distance from the device rotation axis and are subject to bending. In the event of large drilling bit torques, the water supply pipes may break down.
Since the inner surface of the pipeline for delivering water into the hole is different in diameter, the hydraulic resistance of the pipeline increases, thus resulting in higher power expenditure.
In cases where some abrasive material, say, quartz sand is involved, the working surfaces are subject to excessive wear. This primarily applies to the casing of the water and pulp mixing chamber whose repair involves welding, and this results in idle time of the device.